ABSTRACT
As for the last option, the use of both gas and steam turbines is suggested mainly for the ships powered by a single powerful two strokes diesel engine and it becomes profitable when dealing with ship electric power that is 10% superior to the propulsion power. On the contrary, a gas turbine installation for electric generation could be less favorable in that kind of ships that uses four strokes diesel engines, essentially due to the high number of these engines usually adopted onboard. In fact, it is certainly more complex to bypass exhaust gas of many diesel generators (as in passengers ships)
1 INTRODUCTION
In merchant ships, heat recovery is commonly used during sailing to produce the proper steam flow rate required by the several ship consumers (mainly fuel oil heating and hotel service). However, nowadays the usual energy recovery from the exhaust gas boilers is no more sufficient to fulfil the actual-and especially the next-environmental requirements. Moreover, the increasing fuel cost throughout the last years compels marine designers to find new technologies for a better exploitation of the ship whole energy. From this point of view, the main manufacturers of marine machinery (Wärtsilä, MAN, Dresser Rand, MHIMitsubishi Heavy Industries, Siemens) are offering, within their product portfolio, innovative Waste Heat Recovery (WHR) systems. They can be equipped with a steam turbine (powered by the exhaust gas boilers) and/or a gas turbine (fueled bypassing a part of the exhaust gas from the turbochargers of the main diesel engines) for electric or mechanical surplus power generation (MAN Diesel & Turbo 2005, MAN Diesel & Turbo 2010, Wärtsilä 2011).
